/Engine/Source/Runtime/SlateCore/Public/Textures/SlateUpdatableTexture.h
Update the texture from a shared texture handle. The handle type/usage is render system dependent, D3D uses the D3D11 OpenSharedResource call On macOS we use an IOSurface.
void UpdateTextureThreadSafeWithKeyedTextureHandle ( void * TextureHandle, int KeyLockVal, int KeyUnlockVal, const FIntRect & Dirty )